Motor fuel containing synergistic anti-knock additive



United States Patent 3,009,792 MOTOR FUEL CONTAINING SYNERGISTIC ANTI-KNOCK ADDlTIVE George W. Eckert, Wappingers Falls, and Howard V.

Hess, Glenham, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed Mar. 7, 1958, Ser. No. 719,750 12 Claims. (Cl. 44-69) This invention relates to a hydrocarbon fuel composition of high octane rating. More specifically, it involves the discovery that the octane rating of leaded gasoline fuels is substantially improved by the addition of a synergistic additive mixture of a monocarboxylic acid and an aryl amine.

The recent increases in compremion ratios of automobile engines have placed a severe strain on petroleum refiners to produce fuels having the octane rating demanded by these engines. Premium fuels at the present time have research octane ratings between 97 and 100 and it has been predicted that premium fuels will require octane ratings between 105 and 110 five years from now in order to satisfy the octane requirements of the high compression automotive engines predicted for that date. In order to produce premium fuels of octane ratings of 97 and above, it has been necessary for refiners to rely heavily on catalytic refining operations such as fluid catalytic cracking, catalytic reforming, alkylation and catalytic isomerization.

Catalytic cracking and catalytic reforming, which are the most widely used refining operations in the production of high octane fuels, produce substantial quantities of aromatics; catalytic cracking also produces a substantial amount of olefins. It is well-known that olefins and aromatics, although possessing high octane ratings have a poorer response to organo-lead compounds such as tetraethyl lead than saturated aliphatic gasoline components. Accordingly, as the aromatic and olefinic content of the gasolines have increased to meet the octane levels required by modern automotive high compression engines, the lead response of the resulting fuels has diminished. Stated another way, the octane increment obtainable by the addition of an organo-lead compound decreases as the aromatic and olefin contents of the base fuel increase. The subject invention involves the discovery that the octane rating of leaded motor fuels containing a substantial concentration of high octane components, that is, aromatics, olefins and mixtures thereof, is markedly improved by the addition of a small amount of a mixture of a monocarboxylic acid and an arylamine.

Arylamines are well-known anti-knock agents for gasoline. In a commonly assigned copending application Serial No. 689,466, filed October 11, 1957, it is disclosed that monocarboxylic acids substantially raise the octane rating of a motor fuel containing an organo-lead antiknock agent and a substantial concentration of high octane components which may be aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof. The subject invention involves the discovery that a mixture of monocarboxylic acids and arylamines have a synergistic antiknock action in motor fuel compositions of this type.

The high octane hydrocarbon motor fuel of this invention comprises high octane components including a substantial concentration of aromatic hydrocarbons, olefinic hydrocarbons or mixtures thereof, an organo-lead anti-knock agent, a monocarboxylic acid, and an arylamine, both of said latter reagents being present in a concentration of at least 0.1 volume percent of the fuel.

The afore-identified copending application discloses that the action of monocarboxylic acid in raising the octane rating of gasoline is characterized by several unusual "ice features. First, carboxylic acids appear to be ineffective in raising the octane rating of gasolines unless an organolead anti-knock agent, normally tetraethyl lead, is a componenoof the gasoline mixture. Second, equal concentrations of acids appear to cause a greater octane improvement above the 100 octane level than below the 100 octane level. Third, monocarboxylic acids appear to have substantially no efiect on the octane rating of a gasoline consisting essentially of saturated aliphatic hydrocarbons even though an organo-lead anti-knock agent is present. The synergistic anti-knock additive of the invention comprising monocarboxylic acidand arylamine has the same characteristics and, accordingly, is effective in a base fuel containing an organo-lead anti-knock agent 22d a substantial concentration of aromatics and/or ole- The novel fuel compositions of this invention have a minimum concentration of aromatic and/or olefin components of at least 10 volume percent. The aromatic and/or olefin components of the motor fuel of the invention can consitute as high as 100 volume percent thereof but usually fall between 20 and 80 volume percent. A minimum 10 percent concentration is necessary for the synergistic action of monocarboxylic acid and arylamine in improving the octane rating.

The aromatic components of the motor fuel of the invention are generally supplied by catalytic reformin or catalytic cracking operations. Catalytic reformate is particularly high in aromatics. The olefin components of the motor fuel of the invention are derived either from thermal cracking, catalytic cracking or polymerization.

The organolead reagent necessary for the action of a mixture of monocarboxylic acid and arylamine as a synergistic octane improver is a tetraalkyl lead compound of the class known to possess anti-knock action. Tetraethyl lead is practically universally used as an anti-knock agent but other tetraalkyl lead compounds such as tertamethyl lead, tetrabutyl lead, tetraamyl lead, tetrapropyl lead, etc. are known to possess anti-knock properties and may be used in the fuel compositions of the invention in conjunction with a mixture of monocarboxylic acids and arylamines.

The tetraethyl lead mixtures commercially available for automotive use contain an ethylene chloride-ethylene bro mide mixture as a scavenger for removing lead from the combustion chamber in the form of volatile lead halides. As is used hereafter in the examples illustrating the invention, tertaethyl lead fluid" denotes the commercial product which comprises tetraethyl lead, ethylene chloride and ethylene bromide, the latter two reagents being present in 1.0 theory and 0.5 theory respectively, theory denoting the stoichiometric amount required for reaction with the lead content of the tetraethyl lead.

The organo-lead reagent is present in the fuel compositions of the invention in concentrations between 0.5 ml.

per gallon up to the statutory limit of organo-lead reagent concentration which, at the present time, is 3 ml. per gallon in the case of automotive fuel and 4.6 ml. per gallon in the case of aviation fuel. The usual concentration of tetraethyl lead is between 1 and 3 ml. per gallon in automotive gasoline and 2-4.6 ml. per gallon in aviation gasoline.

The monocarboxylic acid component of the synergistic additive of this invention contains 1 to 30 carbon atoms and has the general formula: RCOOH wherein R is hydrogen or a hydrocarbyl radical containing 1 to 29 carbon atoms. Aliphatic monocarboxylic acids, cycloaliphatic monocarboxylic acids, and aromatic monocarboxylic acids all coact with arylamines to form synergistic octane appreciators in leaded fuels containing a substantial aromatic and/ or olefin content.

Monoearboxylic acids that are effective in the fuel compositions of the invention are the following:

Acetic acid, formic acid, propionic acid, caproic acid, n-heptanoic acid, pclargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 2- ethylbutyric acid, 4-methylvaleric acid, 2-ethylhexanoic acid, cumic acid, benzoic acid, cyclohexane carboxylic acid, cinnamic acid, phenylacetic acid,oleic acid, Snodotte acids (hydrogenated fish oil fatty acids comprising mainly C to C acids), and coconut fatty acids (comprising mainly a mixture of C to Cm fatty acids).

Although monocarboxylic acids containing 1 to 30 carbon atoms are effective in the fuel compositions of the invention, the preferred acids contain 1 to 14 carbon atoms and are either aliphatic monocarboxylic acids or aromatic monocarboxylic acids. Preferred acids are 2-ethylhexanoic, benzoic, caprylic, capric, lauric and myristic.

The monocarboxylic acids must be present in the leaded aromatic and/or olefin-containing compositions of the invention in a minimum concentration of 0.1 volume percent before a synergistic octane appreciation with arylamines is realized. With monocarboxylic acid concentrations below 0.1 volume percent, no octane improvement is obtained in leaded gasoline containing at least 10 volume percent aromatics and/or olefins. The preferred concentration of monocarboxylic acid in the synergistic additive falls between 0.2 and 1.0 volume percent with maximum results generally being obtained at a concentration level of about 0.5 volume percent. Concentrations of monocarboxylic acid as high as 5 volume percent can be incorporated in the fuel compositions but no additional synergistic action is realized at the higher concentrations' and economic considerations preclude the use of such concentrations in commercial fuel compositions.

The arylamine component of the synergistic antiknock additive of this invention has the general formula RNHR' wherein R is a monocyclic or bicyclic aryl or alkaryl hydrocarbyi radical containing 6 to 16 carbon atoms and R is hydrogen or a hydrocarbyl radical containing l-l2 carbon atoms. The R radical is normally a monocyclic aryl or alkaryl hydrocarbyl radical. The R radical is usually hydrogen, an aliphatic hydrocarbyl radical containing l-4 carbon atoms or a monocyclic aryl or alkaryl radical in which the alkyl group contains 1-4 carbon atoms. Only primary and secondary arylamines react synergistically with monocarboxylic acids to improve the octane rating of leaded gasoline containing the prescribed aromatic and/or olefin content.

Examples of arylamines which form synergistic antiknock additives with monocarboxylic acids are the following: aniline, N-methyl aniline, N-ethyl aniline, N isopropyl aniline, N-t-butyl aniline, N-n-butyl aniline, otoluidine, p-toluidine, m-toluidine, N-methyl o-toluidine, N-ethyl o-toluidine, Ntbutyl-p-toluidine, diphenylarnine, alphanaphthylamine, di(o-methylphenyl) amine.

The arylamines are employed in a minimum concentration of 0.1 volume percent before a significant synergistic octane improvement is realized with the prescribed concentration of monocarboxylic acid. The preferred concentration of arylamine employed in the synergistic anti-knock additive of the invention falls between 0.2 and 1.0 volume percent. While concentrations of arylamine as high as 5 volume percent can be used in synergistic combination with a monocarboxylic acid, economic considerations preclude the use of such concentrations in commercial fuel compositions. As a practical matter, the upper concentration limit of arylamine is set at approximately 2.0 volume percent.

In Table I there is demonstrated the synergistic antiknock action of monocarboxylic acids and arylamines of prescribed type in a leaded gasoline having the prescribed aromatic and/or olefin content. The base fuel employed in Table I was a commercial premium grade gasoline having an octane rating of 99 and comprising approximately 7 to 10 percent butane, 25-30 percent light fluid catalytically cracked naphtha, 10-15 percent light solventrefined gasoline, 50 percent catalytically reformed naphtha, and 3 cc. of tetraethyl lead fluid per gallon. This base fuel had an aromatic content of approximately 31 volume percent as measured by the Fuorescent Indicator Analysis (FIA) Method. This 99 octane base fuel had an I.B.P. at 92 F. and an end point of 409 F.

Table I Research Octane Number Base fuel 99,0 Base fuel +05% cyclohexane carboxylic acid 99.8 Base fuel +05% 2-ethylhexanoic acid 100.0 Base fuel +0.5 aniline 99.2 Base fuel +05% diphenylamine 99.2 Base fuel +05% alpha-naphthylamine 99.3 Base fuel +05% o-toluidine 99.2 Base fuel +0.5 N-methyl aniline 99.4 Base fuel +05% 2-ethylhexanoic acid 100.7 Base fuel +05% aniline Base fuel +05% Z-ethylhexainoic acid 1003 Base fuel +0.5 alpha-naphthylamine Base fuel +05% 2-ethylhexanoic acid 1008 Base fuel +05% diphenylamine Base fuel +05% Z-ethylhexanoic acid Base fuel +05% o-toluidine 100-8 Base fuel +05% cyclohexane carboxylic acid 101 4 Base fuel +05% N-methyl aniline The data in Table I prove conclusively that monocarboxylic acids and arylamines when employed in the prescribed concentrations have a synergistic anti-knock action in leaded base fuels having the required aromatic and/or olefin content. The octane improvement employing a combination of the arylamine and monocarboxylic acid is almost two octane units whereas the acids alone effect only about a one-unit improvement and the arylamines effect less than a A: unit octane improvement.

In Table II there is shown the syngergistic action of arylamines and monocarboxylic acids as an anti-knock additive in 105 octane gasoline. The base fuel contained 3 cc. of tetraethyl lead fluid per gallon and comprised approximately 10 percent n-butane, 40 percent isobutaneisobutylene alkylate, 10 percent pentenes from fluid catalytically cracked naphtha and 40 percent heavy platformate. This 105 octane base fuel had an aromatic content of approximately 35 percent, an olefin content of approximately 6 percent, an initial boiling point of 90 F. and an end point of 367 F.

Base fuel +05% N-methyl aniline The 4-5 unit octane increments in 105 octane gasoline resulting from the synergistic additive mixtures of benzoic and Z-ethylhexanoic acids with N-methyl aniline are outstanding. The combination of 0.5% benzoic acid with 0.5% N-methyl aniline raised the octane rating of the base fuel 5.3 octane units whereas the individual acid and amine components in 05% concentration raised the octane rating only 3.6 and 0.3 units, respectively. Similarly, the Z-ethylhexanoic acid and N-methyl aniline combination raised the octane rating of the base fuel 4.4 units while the individual acid and amine components raised the octane ratings only 3.0 and 0.3 units, respectively.

In Table HI there is shown the effectiveness of a syn- Table III Research Octane Number Base fuel 966 Base fuel +05% cyclohexane carboxylic acid 98.4 Base fuel +05% N-methyl aniline 97.2 Base fuel +05% benzonic acid 98.2

'Base fuel +05% cyclohexane carboxylic acid Base fuel +05% N-methyl aniline Base fuel +05% benzoic acid 99 6 Base fuel +05% N-methyl aniline The data in Table III further confirm the synergistic action of monocarboxylic acids and arylamines of prescribed formula in raising the octane rating of a leaded gasoline containing a prescribed concentration of aromatics.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing an alkyl lead anti-knock agent, at least 10 volume percent of high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons and mixtures thereof, and a synergistic additive combination of a hydrocarbyl monocarboxylic acid containing 1-30 carbon atoms and a hydrocarbyl amine selected from the group consisting of monocyclic and bicyclic primary and secondary arylamines, said acid and said amine both being present in a concentration of 0.1 to 5.0 volume percent whereby synergistic octane improvement of the octane rating of said organo-lead containing hydrocarbon fuel is obtained.

2. A hydrocarbon fuel according to claim 1 in which the monocarboxylic acid has the general formula RCOOH in which R is selected from the group consisting of hydrogen and hydrocarbyl radicals containing 1-29 carbon atoms.

3. A hydrocarbon fuel according to claim 1 in which said arylamine has the general formula RNHR' in which R is selected from the group consisting of monocyclic and bicyclic aryl and alkaryl hydrocarbyl radicals containing 616 carbon atoms and R is selected from the group consisting of hydrogen and hydrocarbyl radicals containing 1-12 carbon atoms.

4. A hydrocarbon fuel according to claim 1 in which the alkyl lead anti-knock agent is present in a concentration between 0.5 and 4.6 cc. per gallon.

5. A hydrocarbon fuel in the gasoline boiling range containing an alkyl-lead anti-knock agent in a concentration of at least 0.5 cc. per gallon, high octane components selected from the group consisting of olefinic hydrocarbons, aromatic hydrocarbons, and mixtures thereof in a concentration of at least 10 volume percent of said fuel, a synergistic additive combination of a monocarboxylic acid of the general formula RCOOH in which R is selected from the group consisting of hydrogen, and hydrocarbyl radicals containing 1-14 carbon atoms and an arylamine of the general formula RNHR' in which R is selected from the group consisting of monocyclic and bicyclic aryl and alkaryl hydrocarbyl radicals containing l6 carbon atoms and R' is selected from the group con sisting of hydrogen and hydrocarbyl radicals containing 1-12 carbon atoms, said acid and amine components both being present in concentrations of 0.1 to 5.0 volume percent whereby a substantial improvement of the octane rating of said hydrocarbon fuel is effected.

6. A hydrocarbon fuel according to claim 5 in which said acid and amine components constitute 0.2 to 1.0 volume percent of said fuel.

7. A hydrocarbon fuel accordihg to claim 5 in which said additive combination comprises 2-ethylhexanoic acid and aniline.

8. A hydrocarbon fuel according to claim 5 in which said additive combination comprises 2-ethylhexanoic acid and alpha-naphthylamine.

9. A hydrocarbon fuel according to claim 5 in which said additive combination comprises 2-ethylhexanoic acid and N-methyl aniline.

10. A hydrocarbon fuel according to claim 5 in which the additive combination comprises benzoic acid and N- methyl aniline.

11. A hydrocarbon fuel according to claim 5 in which the additive combination comprises cyclohexane carboxylic acid and N-methyl aniline.

12. A hydrocarbon fuel according to claim 5 in which the additive combination comprises Z-ethylhexanoic acid and o-toluidine.

References Cited in the file of this patent UNITED STATES PATENTS 1,605,663 Kettering et a1. Nov. 2, 1926 1,606,431 Hamby et al. Nov. 9, 1926 1,649,485 Orelup Nov. 15, 1927 1,692,784 Orelup Nov. 20, 1928 2,230,844 Miller et a1 Feb. 4, 1941 2,403,268 Davis et a1. July 2, 1946 2,409,156 Schulze et a1. Oct. 8, 1946 2,884,315 Barnum Apr. 28, 1959 FOREIGN PATENTS 277,326 Great Britain Jan. 7, 1929 640,311 France :2 July 10, 1928 793,967 France t Feb. 5, 1936 837,965 France .i Feb. 23, 1939 OTHER REFERENCES Improved Motor Fuels Through Selective Blending, Wagner et al., American Petroleurn'lnstitute, November 7, 1941. 

1. A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE CONTAINING AN ALKYL LEAD ANTI-KNOCK AGENT, AT LEAST 10 VOLUME PERCENT OF HIGH OCTANE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF OLEFINIC HYDROCARBONS, AROMATIC HYDROCARBONS AND MIXTURES THEREOF, AND A SYNERGISTIC ADDITIVE COMBINATION OF A HYDROCARBYL MONOCARBOXYLIC ACID CONTAINING 1-30 CARBON ATOMS AND A HYDROCARBYL AMINE SELECTED FROM THE GROUP CONSISTING OD MONOCYCLIC AND BICYCLIC PRIMARY AND SECONDARY ARYLAMINES, SAID ACID AND SAID AMINE BOTH BEING PRESENT IN A CONCENTRATION OF 0.1 TO 5.0 VOLUME PERCENT WHEREBY SYNERGISTIC OCTANE IMPROVEMENT OF THE OCTANE RATING OF SAID ORGANO-LEAD CONTRAINING HYDROCARBON FUEL IS OBTAINED. 